1. Field of the Invention
This invention relates generally to the fabrication of transmit/receive (T/R) modules used in connection with the aperture of an active electronically scanned array, and more particularly to the plating of RF connectors brazed onto the front side of high temperature co-fired ceramic (HTCC) substrate of a T/R module package.
2. Description of the Prior Art
The process of brazing RF connectors onto the side of an HTCC package involves re-flowing the high temperature alloy of copper and silver (Cusil) to provide a robust mechanical attachment of the center pin and shroud of the RF connector to a substrate member of a T/R module shown, for example, in U.S. Pat. No. 6,114,986, entitled “Dual channel Transmit/Receive Module For An Active Aperture Of A Radar System”. The materials involved in this operation, Kovar for the center pin and shroud and Cusil brazing material, are prone to corrosion and therefore require gold plating to prevent corrosion in any non-hermetic environment. Plating of this part involves first nickel plating and then gold plating. Any non-plated area on the center pin area can result in corrosion of the center pin and loss of the RF signal, resulting in a catastrophic failure of the entire T/R module package.
The present state of the art for fabrication/assembly of a connector onto a T/R module package typically involves brazing the center pin and shroud of the connector as stated above. The shroud is currently an elongated solid structure including a plurality of generally cylindrical apertures through which the center pins project and which is required to connect the ground signal of the mating structure, i.e., the connector. During the plating process, the module package is placed in plating baths of nickel followed by gold. For proper plating, i.e., complete plating to occur, the solution must flow throughout the interior of the connector shroud. However, this does not often occur due to the inherent physical features of the inner walls of the connector shroud. It has been found that due to the lack of good plating solution flow throughout the interior of the RF connector, a relatively large number of packages have been rejected because of unplated areas around the connector center pins. The pins do not have proper plating, for example, where the pin is brazed to the ceramic package. This plating deficiency occurs as a result of a lack of flow of the plating solution within the connector.
Since plating is performed at the end of the package fabrication process, a rejection of the package results in a loss at the most expensive point in the process of a finished product. Thus an unreasonable number of failures in a production system using this type of RF interconnect can result in a relatively large increase in the overall cost of acceptable or “good” T/R module packages.